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931.
E. Betranhandy Samir F. Matar Ch. El‐Kfoury R. Weihrich J. Etourneau 《无机化学与普通化学杂志》2004,630(15):2587-2598
The changes in electronic structure and hardness as inferred from the bulk modulus are investigated for model structures of ternary compounds XC3N3 (X = B, Al, P, As, Ga) within the framework of density functional theory (DFT). The optimisations of the proposed two‐ (2D) and three‐dimensional (3D) structures and the calculations of the bulk moduli are performed by a pseudo potential method. The electronic structures are calculated with the augmented sphere wave method (ASW). The obtained hardness for 2D BC3N3 system (B0 ~ 220 GPa) points to a magnitude close to that of graphitic C3N4. For heavier X atoms it decreases rapidly. This is equally observed for the 3D systems examined in the β‐C3N4 structure for which B0(β‐BC3N3) amounts to ~330 GPa. Within the magnitude of the well known hard material cubic BN, the BC3N3 phases can be predicted as candidates for ultra hard materials. The electronic effect induced by the chemical nature of the X substitutional was examined according to its position in the periodic table i.e. XIII or XV. Both, band structures and the electron localisation function (ELF) were used for this analysis. The ELF plots show a decreasing covalency with heavier X‐atoms. Potential applications of the devised systems are proposed such as dopings with atoms (Li, rare gas) and molecules (N2). 相似文献
932.
933.
A new phosphorylcholine, (6-hydroxy) hexyl-2-(trimethylammonio) ethyl phosphate (HTEP), was synthesized andcharasterized. Segmented polyurethane (SPU) containing phosphorylcholine structure was synthesized based ondiphenylmethane diisocyanate (MDI), soft segment polytetramethylene glycol (PTMG) and HTEP, with 1,4-butanediol (BD)as a chain extender. The existence of phosphorylcholine structure on the surface of SPU was revealed by attenuated totalreflectance Fourier transform infrard spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and water contactangle measurements. The blood compatibilities of the polymers were evaluated by hemolytic testing and a platelet-richplasma (PRP) adhesion experiment, which was viewed by scanning electron microscopy (SEM) with polyurethane as areference. The novel segmented polyurethane containing phosphorylcholine structure showed improved blood compatibility. 相似文献
934.
935.
Lin Guo-qiang Xu Hai-jian Wu Bi-chi Guo Guong-zhong Zhou Wei-shan 《Tetrahedron letters》1985,26(9):1233-1236
All the four optical isomers of the oviposition attractant pheromone of the mosquito were synthesized via Sharpless asymmetric epoxidation. 相似文献
936.
The electrical transport and magnetic properties of BaVS3, made up of individual VS3 octahedral chains, were examined on the basis of first principles and tight-binding electronic structure calculations. The electrical conductivity of BaVS3 is nearly isotropic despite its one-dimensional structural feature, because of the orbital interactions associated with the short S···S contacts within each VS3 chain and between adjacent VS3 chains. The probable cause for the metal-insulator transition at ∼70 K was examined in terms of first principles electronic structure calculations, which indicate that the metallic and magnetic insulating states of BaVS3 are nearly the same in energy. This is consistent with the observation that the metal-insulator transition at ∼70 K is caused by electron localization. The observed magnetic properties of BaVS3 below ∼70 K are readily explained under the assumption that the symmetry-broken t2g-orbitals act as the magnetic orbitals in the magnetic insulating state of BaVS3. The probable cause for the latter was discussed. 相似文献
937.
Houda Marouani Mohamed Rzaigui Muriel Bagieu‐Beucher 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(3):356-357
In hexakis(m‐toluidinium) cyclohexaphosphate, 6C7H10N+·P6O186?, the atomic arrangement is typical of a layer structure. Layers including the centrosymmetric P6O18 ring anions develop around the (100) planes at x = . The hydrogen‐bond distribution is described. 相似文献
938.
Zachary M. Schulte Yeon Hye Kwon Yi Han Chong Liu Lin Li Yahui Yang Austin Gamble Jarvi Sunil Saxena Gtz Veser J. Karl Johnson Nathaniel L. Rosi 《Chemical science》2020,11(47):12807
Metal–organic frameworks constructed from multiple (≥3) components often exhibit dramatically increased structural complexity compared to their 2 component (1 metal, 1 linker) counterparts, such as multiple chemically unique pore environments and a plurality of diverse molecular diffusion pathways. This inherent complexity can be advantageous for gas separation applications. Here, we report two isoreticular multicomponent MOFs, bMOF-200 (4 components; Cu, Zn, adeninate, pyrazolate) and bMOF-201 (3 components; Zn, adeninate, pyrazolate). We describe their structures, which contain 3 unique interconnected pore environments, and we use Kohn–Sham density functional theory (DFT) along with the climbing image nudged elastic band (CI-NEB) method to predict potential H2/CO2 separation ability of bMOF-200. We examine the H2/CO2 separation performance using both column breakthrough and membrane permeation studies. bMOF-200 membranes exhibit a H2/CO2 separation factor of 7.9. The pore space of bMOF-201 is significantly different than bMOF-200, and one molecular diffusion pathway is occluded by coordinating charge-balancing formate and acetate anions. A consequence of this structural difference is reduced permeability to both H2 and CO2 and a significantly improved H2/CO2 separation factor of 22.2 compared to bMOF-200, which makes bMOF-201 membranes competitive with some of the best performing MOF membranes in terms of H2/CO2 separations.Tailorable multicomponent MOFs and MOF membranes for efficient H2/CO2 separation. 相似文献
939.
940.